Modern cellular digital mobile communications networks have revolutionized mobile communication since the beginning of the 1990s. They have almost completely replaced the existing analog mobile communications networks. Modem standards (in particular GSM, UMTS, CDMA) facilitated a drop in infrastructure and terminal device prices, which led to competition among the telephony providers and to lower charges.
Competition among the companies manufacturing the infrastructure was also promoted as a result of the fact that communication between the network elements was standardized and the interface descriptions and protocols were laid open, consequently enabling mobile communications networks conforming to the aforementioned standards to be built by putting together network elements supplied by any manufacturers. A feature common to all mobile communications networks is that they consist of elements for providing radio coverage (antennas, base stations (in the case of GSM, called “BTS”—Base Transceiver Station), control units (in the case of GSM, called “BSC”—Base Station Controller) and of elements from switching technology (in the case of GSM, called “MSC”—Mobile Switching Center). In addition there exist various other network elements for accomplishing diverse tasks such as providing a connection to the public telephone system (PSTN), user management and the like.
In the development of these standards attention was focused on providing coverage for the urban and rural area, with cell sizes and interfaces being geared to distances and user densities typical therefor.
If there now exists the desire for mobile communication in areas cut off from conventional infrastructure, such as e.g. remote islands, settlements, aircraft and ships, a possible approach is to set up a complete mobile communications system at said locations and to attach them to the public telephone system by way of, for example, telephone cables, directional radio relay links or satellite radio links. This is associated with very high costs, however. In the case of the use of such a system in an aircraft, the considerable weight of said equipment also constitutes a problem.
If, instead, only the absolutely necessary network elements (terminal devices, base station) are brought to these remote locations and the connection to the rest of the mobile communications system is routed via a transmission system, then the question arises as to how to transfer the connection of said exposed network elements to the rest of the mobile communications system. In principle this problem can be solved; corresponding data links can be set up without problems to practically any location worldwide.
Communication between mobile communication subscribers within a remote area of said kind subjects the connection to the control units to load without the transmission of data, generally voice data, as far as the switching technology elements actually being necessary. The data stream accruing in the process reduces the remaining transmission capacity for connections for which the transmissions on said interface are absolutely essential. Only data that is required for signaling purposes needs to be transported in every case as far as the switching technology elements.
According to the prior art said object is achieved by means of an evaluation of the signaling data, wherein either a central network element performs the corresponding control functions in the affected base station or a base station keeps a list of the subscribers registered in each case (HLR function) and itself performs the corresponding control functions. (WO2007/069229) Other solutions are described, for example, in US2006/0154660 or EP0797312.